1. Field of the Invention
This invention relates to a method of removing solids from a viscous hydrophobic feed stream containing solids. More particularly, it relates to a method for removing solid particles from a viscous synthetic hydrocarbonaceous liquid, such as at least a fraction of an original syncrude.
2. Description of the Prior Art
The problem of separating solids from a feed stream is an old one; and the art is replete with a variety of apparatus and methods for accomplishing the separation. For example, solid bowl centrifuges, perforate bowl centrifuges and the like have been employed to separate solids from drilling muds, either water based muds or oil based muds. Moreover, other industries have encountered this problem and have resolved it by a variety of different methods and apparatus. One broad industrial process that has had a severe problem of separating the solids from the feed stream is that of producing a synthetic hydrocarbon, usually called syncrude, or the more viscous fractions thereof. For example, syncrudes have been produced from coal, tar sands, oil shale and the like. Generally, these syncrudes have had intolerably high amounts of solids, such as the sand, oil shale, coal ash, carbon particles, and the like in the syncrude. Accordingly, when the syncurde was syncrude into its various fractions by appropriate techniques, at least one of the more viscous fractions would contain these solids. Discard of these fractions having the intolerably high portion of solids therein created a pollution problem and, also, resulted in a loss that adversely affected an already marginally feasible process. Even the increased recent emphasis on additional sources of energy have not alleviated this problem. Instead, it has made more desirable the provision of a method of recovering the desirable portions of the syncrude fraction while minimizing the losses in the solids phase for economical and ecological reasons.
Specifically for shale oil, processed shale must be removed from crude shale oil in order to produce either a low ash coke or a low ash fuel oil. In a typical shale oil recovery process, the processed shale (solids) is concentrated in a heavy fraction of the shale oil. No satisfactory method for removing these solids from this shale oil has been provided heretofore, since conventional filtration and/or centrifugation processes alone are inadequate.
Discarding the solids-containing fraction without removing the solids is not only wasteful by wasting the shale oil fraction content, but is unsafe and is a pollution factor that must be reckoned with in dealing with the regulatory agencies of the government.
Typical of the wide variety of patents for producing syncrudes and finally ending up with a fraction that had an undesirably high proportion of syncrude fraction in the waste product are the following patents: U.S. Pat. Nos. 2,420,376; 3,025,223; 3,350,200; and 3,841,993. In all of these processes, the waste products could have employed to advantage the method of this invention.
Thus, insofar as I am aware, the prior art has not provided a satisfactory method of separating the solids from the viscous streams of liquid, such as the viscous synthetic hydrocarbon fractions.